Process for recovering used lubricating oils using clay and centrifugation

ABSTRACT

A process for recovering used lubricating oils, and oils recovered using the process. In a first embodiment (for used industrial oils), the used lubricating oil is mixed with clay in a reactor. The mixture is preferably heated to between 80 and 200 degrees Celsius. The temperature should not be too great, to avoid “cracking” the oil (i.e., breaking molecular chains in the oil). After a certain period of time, the mixture is pumped through filters. Cakes of clay and contaminants remain in the filters, while the oil emerges without the contaminants. A second embodiment (for removing ash or soot, very fine carbon particles and other organic compounds from used motor oils) is the same as the first embodiment, except that before the mixture is passed through the filters, a centrifuge is used to remove most of the clay contaminated with soot, so that it will not block the filters.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the removal of contaminants fromindustrial used lubricating oils and used motor oils by treatment of theused oil with clay at high temperatures, but at lower temperatures thanthat of “cracking”, and later removing the contaminated clay byfiltration and centrifugation.

2. Description of the Prior Art

The recycling of used lubricating oils coming from industrial processes,car motors, transmissions and other sources is an important process,because it avoids contamination by lubricating oils, and allows therecovery of lubricating base oils, which are a scarce product. The oilsform a monomolecular layer on the surface of the water, which it meansthat a small quantity of oil can contaminate a great volume of water.

The recovered lubricating oil bases have all the properties of the firstrefining, and they can be used to produce new oils. The recyclingprocess can be done several times.

The contaminants in industrial oils, besides water, are usually iron,chromium, cadmium, nickel, copper, calcium, barium, zinc, aluminum, andphosphorus. Motor oils also have soot, contaminants due to degradedadditives, and other contaminants coming from the gasoline, and for thatreason they are more difficult to be re-refined.

Several techniques have been used to re-refine used oils, mainly bydistillation and treatment with chemical reactives to precipitate thecoagulants (principally sulfuric acid and other solvents, which are alsocontaminants that produce environmental problems).

The treatments with clays at very high temperature have the problem thatthe later separation becomes difficult because the pores of the felt(cloths, cellulose, synthetic materials or others) of the filter pressbecome plugged, mainly due to soot, colloidal coal, and organiccompounds.

The distillation systems require large investments, and the re-refiningcost is usually expensive. This is also the case of the other usedtreatments with sulfuric acid, sulfates, phosphates and other chemicals,which are difficult to extract later on. For example in the separationof sulfuric acid with clays there is the inconvenience of the greatproduction of sludge, besides the large volumes of corrosive acids andthe great lost of used original oils. It is necessary to take intoaccount that the pre-heating of the mixtures must not be higher than250° C. to 300° C., if one wants to avoid the “cracking” of thelubricating oils. (Excessive heat causes hydrocarbon chains in the oilto “crack” and break into smaller chains, which are not suitable forlubricating oil, though they may be suitable for fuel oil.) Other moreeconomic systems use inorganic catalysts mixed with clays in continuousfeeding systems.

The present invention has important advantages with respect to theseprocesses.

U.S. Pat. No. 3,625,881, issued on Dec. 7, 1971, to John M. Chambers andHerbert A. Hadley, discloses a process for reclaiming lubricating oils,including flash vaporization to remove water, mixing the used oil with ahydrocarbon oil, using a centrifuge to remove solid precipate, and twofractional distillations. The instant invention is distinguishable, inthat in it the used oil is mixed with clay rather than another oil.

U.S. Pat. No. 3,639,229, issued on Feb. 1, 1972, to Darrell W.Brownawell and Remi H. Renard, discloses a process of refining usedlubricating oils, in which the used oil is mixed with aliphatic alcohol.There may be a final clay treating step (see claim 9). The instantinvention is distinguishable, in that it does not require the use ofalcohol.

U.S. Pat. No. 3,819,508, issued on Jun. 25, 1974, to Morton Fainman andCharles Stouse McCauley, discloses a method of purifying lubricatingoils, in which the oil is mixed with a predominantly hydrocarbon liquiddiluent, then with an alcohol and water mixture, and centrifuging isused to remove sludge and metal compounds. The instant invention isdistinguishable, in that in it the used oil is mixed with clay.

U.S. Pat. No. 3,919,076, issued on Nov. 11, 1975, to Louis E. Cutler,discloses a process for re-refining used automotive lubricating oil,including treatment with a saturated hydrocarbon solution, followed byvacuum distillation, followed by catalytic hydrogenation, which are notrequired in the instant invention.

U.S. Pat. No. 3,930,988, issued on Jan. 6, 1976, to Marvin M. Johnson,discloses a process for reclaiming used motor oil using an aqueoussolution of ammonium sulfate or bisulfate, which is not required in theinstant invention.

U.S. Pat. No. 4,033,859, issued on Jul. 5, 1977, to Donald DouglasDavidson and Bjorn I. Engesvik, discloses thermal treatment of usedpetroleum oils under pressure at temperatures to above about 400 to 800degrees Fahrenheit (or 190 to 412 degrees Celsius). Although there is asmall overlap in the temperature range, the instant invention does notrequire pressure during its heating step.

U.S. Pat. No. 4,383,915, issued on May 17, 1983, to Conrad B. Johnson,discloses a clay contacting process for removing contaminants from wastelubricating oil, in which the oil is contacted with decolorizing clay ata temperature in the range of 650 to 725 degrees Fahrenheit (or 329 to370 degrees Celsius). The instant invention is distinguishable, in thatit uses a lower temperature range, and a different type of clay (seecolumn 3, lines 21 to 31).

U.S. Pat. No. 5,112,479, issued on May 12, 1992, to VichaiSrimongkolkul, discloses an oil purification unit with a cyclonic(centrifuge) reservoir section and a filtration section. The secondembodiment of the instant invention is distinguishable, in that in itthe oil is first mixed with clay before being centrifuged.

U.S. Pat. No. 5,759,385, issued on Jun. 2, 1998, to Marcel Aussillous etal., discloses a process and plant for purifying spent oil, includingvacuum distillation, which is not required by the instant invention.

U.S. Patent Application Publication No. 2006/0000787, published on Jan.5, 2006, to Louis Galasso III et al., discloses purification of impureoil by centrifugation, without first mixing the oil with clay as in theinstant invention.

French Patent No. 2 690 924, published on Nov. 12, 1993, to VirgulinoAntonio Digilo, discloses a method of re-cycling of used or contaminatedlubricating oils, including adding clay to the oil in a reactor, andalso adding water containing a dissolved sulphur based catalyst andfiltration aid. The instant invention is distinguishable, in that itdoes not require adding water with a catalyst.

Japanese Patent No. 2-4898, published on Jan. 9, 1990, to KyohoSeisakusho and Toyota Jidosha, discloses a process of reclaiminglubricating waste oil, including a thermal reaction treatment in whichan aqueous solution of caustic alkali is added to the oil, acentrifugation process after diatomaceous earth and activated clay areadded to the oil, and a filtration process. The instant invention isdistinguishable, in that it does not require that the addition of asolution of caustic alkali to the oil.

None of the above inventions and patents, taken either singly or incombination, is seen to describe the instant invention as claimed.

SUMMARY OF THE INVENTION

In our search for a process for the recovery of used lubricating oilsthat was economic and did not require high investments, a fact to beconsidered appeared immediately. It was necessary to separate thetreatment of industrial oils, with mainly watery and metalliccontaminants, from those with organic contaminants and soot, such asthose coming from the internal combustion motors. For this reason, thepresent invention has two preferred embodiments: the first for recoveryof used industrial lubricating oils, and the second for recovery of oilscoming from internal combustion motors (including used lubricants oilsof explosion and diesel motors, automatic transmissions, and in general,every kind of oils coming from filling and service stations for cars).

The first preferred embodiment of the present invention is suitable forused industrial oils, and it includes the steps of: (a) Mixing the usedlubricating oils with clay in a reactor, and heating the mixture totemperatures from 80° C. to 200° C., in a batch type system. Thetemperatures are low enough that the cracking of the lubricating oils inthe mixture does not take place or at least is minimized. (b) Keepingthe mixture of clay and used lubricating oil for a certain residencetime in the reactor. (c) Filtration by a system of filter presses,wherein the clay sticks to the filtering cloths, and the filtered oilgoes through free of impurities. This system is shown in FIG. 1, whichcorresponds to the first preferred embodiment.

An important observation in this process is that, if this is performedin a continuous way, with feeding of used oil and preheated clay throughthe bottom of the reactor and gathering of recovered oil from the upperside, then the oil still contains a large amount of contaminants, and isnot suitable for future use. In continuous systems in the prior art,they use catalysts or chemical reactives to obtain suitable results,which complicate and increase the cost of the process.

On the other hand, it is important also to point out that the amount ofwater contained in some oils is high, and in these cases before addingthe clay it is convenient to eliminate the water with a “flash”distillation process from 80° C. to 100° C., prior to treatment with theclay.

The second preferred embodiment of the invention is designed for theremoval of metallic contaminants, soot and organic contaminants from theused lubricating oils coming from automotive market. It includes thesteps of: (a) Mixing the used lubricating oils with clay in a reactor,and heating the mixture to temperatures from 80° C. to 200° C. Again,the temperatures are low enough that the cracking of the lubricatingoils in the mixture does not take place or at least is minimized. (b)Keeping the mixture of clay and used lubricating oil is for a certainresidence time in the reactor. (c) Using a centrifuge to separate alarge part of the oils to be recovered from the clay containing organicand metallic contaminants. (c) Filtration of the oils coming from thecentrifuge, by passing them through a filter press as described abovefor the industrial used oils. The second preferred embodiment isillustrated in FIG. 2.

For both embodiments, the heating system which was found most economicfor the process of the present invention, consists of a boiler heatedwith gas and a transference fluid (e.g., hydraulic oil), which carriesthe heat from the boiler to a heating jacket in the reactor containingthe used oil and clay. The heating is done by conduction. The usedlubricating oils are loaded in the reactor with movable and diaphragmelectric pumps, or by gravity. Before the used oils are placed into thereactor, they may be passed through a gross filter (for instance, 200mesh) to remove large particles. After passing them through the grossfilter, there can also be a flash distillation from 80° C. to 120° C. toremove excessive quantities of water. Next, the right amount of clay isadded, and after some residence time determined by the type of oil andlaboratory analysis, the mixture in the reactor is discharged. Duringthe residence time the clay reacts with the contaminants, creatingchemical bonds between them. For this, it is necessary to have goodcontrol of the temperature (in order to avoid cracking the oils) and ofthe amount of clay and the residence time in the reactor. All theseconditions are previously determined by the laboratory analysis. Afterthat the filtering process is performed.

Accordingly, it is a principal object of the invention to provide animproved process for recycling industrial lubricating oils.

It is another object of the invention to provide an improved process forrecycling automotive lubricating oils.

It is a further object of the invention to reduce pollution to theenvironment from discarded used lubricating oils.

Still another object of the invention is to reduce the depletion ofnonrenewable resources used in making lubricating oils.

It is an object of the invention to provide improved elements andarrangements thereof in an apparatus for the purposes described which isinexpensive, dependable and fully effective in accomplishing itsintended purposes.

These and other objects of the present invention will become readilyapparent upon further review of the following specification anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the first preferred embodiment of theinvention.

FIG. 2 is a schematic diagram of the second preferred embodiment of theinvention.

Similar reference characters denote corresponding features consistentlythroughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention an improved process for recycling used lubricatingoils, having two preferred embodiments.

The FIG. 1 depicts the first preferred embodiment of the process of theinvention, which is its simplest form. The concept discussed is a“batch” or “semi-batch” type process, wherein the used contaminatedlubricating oil 10, which may be filtered before going to the reactor12, is mixed with activated clay 14 to high temperature, obtained bymeans of a heating jacket 16 in the reactor. To maintain the temperatureof the heating jacket, hot hydraulic oil can be used as a heattransference fluid, which is heated in a boiler (not shown in thedrawings). The operation of mixing oil with clay and heating can be donein a continuous way, but the best results are obtained with the “batch”or “semi-batch” non-continuous system. The reactor, where theinteraction between the clays and the oil to be recovered is takenplace, usually has stirring rods 18, which allow a faster process anddecrease the residence time. The residence time can be from severalminutes to several hours, depending on the type of oil and contaminants.Before loading the reactor, it may be desirable to perform a flashdistillation, to eliminate the water that is coming with the used oils,as well as a pre-filtration to eliminate contaminants of large size.From the reactor, the heated oil-clay mixture is pumped using pump 20through a filter press 22 where the clay and trapped contaminants areseparated from the oil. The clay is left in the filters 24 as a “cake”,and the recovered oil without contaminants is carried out to a pipesystem 26, which retake the filtered oil from the filter press. Afterloosening the filtered frame with its filters, the clay cake sticks tothe filters, but is separated from them, in order to recover thefilters, leaving the clay as waste material 28. The recovered oil, nowwithout contaminants, can be used as lubricating base oil.

In FIG. 2, showing the second preferred embodiment of the invention, theprocess is similar to that depicted in FIG. 1, but now there is anindustrial centrifuge 30 between the reactor 12 and the filter press 22.The reason for this centrifugal system is that for the used oils comingfrom explosion motors, an important contaminant is the soot, whichcomprises very small particles of carbon and other organic compounds,such as the additives of the lubricants. The problem with thesecontaminants is that when they are taken directly to the filter press,they plug the pores of the filter felts (cloths, cellulose, synthetic,etc.), stopping or decreasing very strongly the filtered flow. It is forthis reason that a centrifugal operation is needed prior to filtration,in order to remove most of the clay contaminated with soot 32, in orderto allow a filtered operation later without problems.

The system described in FIG. 1 is suitable for the recovery ofindustrial oils with low or no contamination with soot or organicproducts, and the system described in FIG. 2 is mainly appropriate forused oils coming from cars and motor vehicles, where there is a highpercentage of soot contamination. However, this more complete secondsystem can be also used for industrial oils or any kinds of used oils,e.g., oil used in internal combustion motors, or in industrial or othermotors.

Once the recovered bases are obtained, the corresponding analysis has tobe performed in order to determine that the amount of contaminants isbelow the wanted level, as well as to determine the characteristics ofthe recovered base lubricating oils, such as their viscosity, totalbasic number (TBN), flash point, etc.

The following examples are given for illustration:

Example 1 A treatment of 1,800 liters of used oil of industrial originwas performed, to show the effectiveness of the present invention.Process of Recovery of Used Industrial Oils (Example Industrial Plant)Materials.—

1,800 liters of lubricating oils for industrial gears coming fromCarbonorca Enterprise C.A.

Initial Characteristics of the used Oils.— 1. Color: Opaque brown,non-translucent.

2. Presence of free water and/or in emulsion: (10-50% v/v).

3. Presence of solid suspended particles (>1000 mg/Kg, 0-30% v/v)

4. pH: >7

5. Aromatics: <1 mg/Kg. 6. Solvents: 0-10% v/v. System ofAbsorbent/Adsorbent.—

Activated clays, hybrid type of hormite and smectite, with acidcharacteristic, with pH (5% solids diluted in H₂O) equal to 2.5-3.0,density of 336-416 g/l, and particle size, by sieve analysis (TylerStandard), particles with sizes less than 150 μm: 100%, and particleswith sizes less than 45 μm: of 73-76%.

Procedure Description.—

-   -   1) Pre-filtration: The used industrial oil goes through mobile        filtering equipment to eliminate big particles that could be        present in the oils. Polyester sleeve filters with holes of        10-100 microns were used.    -   2) Reactor load: Mobile pumps were used for the process of        loading the 1,800 liter batch.    -   3) Distillation flash: The oil was heated with a system of        thermal oil recirculation coming from a boiler, with the aim of        eliminating the water and the residual part of the solvents. The        temperature reached oscillates between 105-115° C., measured and        controlled with instruments installed in the reactor (i.e.,        thermocouples and flow control valves). Time of heating averaged        two hours. In this stage the oil is recirculated and there is a        continuous mechanical stirring. Once the distillation        temperature is reached and the water eliminated, a crackling        test (ECC001) is performed to be sure that there is no water        remaining.    -   4) Absorption/Adsorption Process: Once the crackling test is        performed, the absorbent/adsorbent elements, namely the clays,        are added in the reactor. The amount to be used is determined        previously by the laboratory tests. The addition of these        different elements varies between 0.5-2% v/v for a batch of 1800        liters. (By “v/v” is meant the volume of clay divided by the        total volume of the mixture in the reactor.) For lower loads of        this amount and/or more contaminants the clays added could be in        the range of 2-5% v/v. There is stirring during the addition of        the clays, and once they are added, the stirring continues        simultaneously with the recirculation to get an optimums contact        between the oil and clay. This process lasts for a period of        five to fifteen minutes. (Note that absorption means drawing        into the interior of the clay particles, adsorption means        attachment to the surface of the clay particles, and absorption        and adsorption are collectively referred to as “sorption”.)    -   5) Filtration Process: Once the period of clay-oil mixture is        finished, the filtration process is started. This is performed        with a filter press of vertical plates provided with a series of        100% cotton cloths with openings between 10-40 microns and a        100% cellulose filter of 8-20 microns holes. The operation        pressures are 30-100 psi at the entrance of the filter and 10-15        psi at the exit. The amount of solid particles in the filtration        process is analyzed to guarantee that the final oil does not        contain any solids.        Once the removal of contaminants is finished the procedure is:    -   1) Passing the recovered lubricating base oil to the observation        tank (checking previously that there are not solid particles).        The observation tank has a preventive function, since it enables        the determination of the location of any possible contamination        with solid particles or high levels of metals, if the removal        process becomes inefficient for any reason.    -   2) There is a metallic characterization by the method of atomic        absorption to determine if the product is good to be used to        produce lubricants.    -   3) Once the two preceding steps are done, viscosity and        viscosity index are determined with the aim of storing in        lubricating plant tanks, to decide which kind of use will be        assigned. There is a pumping system connected to a series of        pipes and valves, wherein the recovered lubricating base oils go        through post-filters, to insure that there is not any type of        residue or solid particle.        Table 1 shows the analysis of properties of industrial used oil:

TABLE 1 Initial Properties of Used Oil Before the Process ParameterUnit* Value Method Cadmium and composites mg/Kg <0.10 ASTM D 5185Chromium and composites mg/Kg 14.4 ASTM D 5185 Soluble copper compositesmg/Kg 22.1 ASTM D 5185 (salts and acids) Nickel and composites mg/Kg3.51 ASTM D 5185 (salts and acids) Lead and composites mg/Kg 534.9 ASTMD 5185 (salts and oxides) Vanadium and composites mg/Kg 8.9 ASTM D 5185(salts and oxides) PCBs ppm <0.10 HGPC Sediments ml/L <0.10 ASTM D 473R²—Cl** ppm 800 9077 Cinematic Viscosity to cSt 18.6 100° C. Densityg/cm³ ASTM D 1298 Flash Point ° C. 195 NVC 372 H₂O by distillation % p/v0.00 ASTM D95 Total Sulfur % p/p 0.60 ASTM D 1552 *1 mg/Kg = 1 ppm**R²—C1 = Organic RadicalTable 2 presents the properties of the recovered lubricating base oilsobtained through this process:

TABLE 2 Final Properties of Recovered Oil (Lubricating Bases) After theProcess Obtained Parameter Unit Specification value Method FlashPoint °C. 210-260 219 Covenin 372 Method of open cup Cinematic Viscosity to cSt15-19 17.4 Covenin 424 100° C. Viscosity Index 90 Covenin 889 Calciumppm <0.01 0.005 Covenin 2044 Magnesium ppm <0.014 0.009 Covenin 2044Zinc ppm <0.1 0.02 Covenin 2044 Crepitating, crackle S/N NegativeCovenin Specific Gravity to g/ml 0.8685 0.8703 Covenin 15.6° C. Amountof clay S/N Negative Method EC- B05

Example 2

A laboratory experiment was performed, with a sample of used motor oil.The following is a description of the details of the experiment:

Materials:

800 ml of used oil, coming from a Fiat “Ritmo” car, 1987 model, 1600 mlmotor, with 45 days of running, and a total of 55,000 km passed over.The original oil was PDV (Petroleum of Venezuela) brand, 20W-50Wmultigrade (Experiment No. 1). There was also used 800 ml of a mixtureof used oils coming from an workshop for oil change, located in Maracay,Aragua State-Venezuela (Experiment No. 2).

System of Absorbent:

Activated clays, hybrid type of hormite and smectite, with acidcharacteristic.

Experimental Process and Preparation of Samples for Analysis:

A sample of 800 grams of used motor oil was put in a glass beaker, witha magnetic stirrer inside, and was placed on an electric heating platewith continuous magnetic stirring.

The heating of the sample was between 100-120° C. during 30 minutes, inorder to eliminate the water, until the crepitating or crackling testwas negative. The amount of clay was prepared in approximately 20% m/mof used oil. (By “m/m” is meant the mass of the clay divided by mass ofthe used oil.) The oil was added with stirring of 800 to 1200 rpm,during one hour, and reaching temperatures of 180° C.

The mixture oil-clay was passed through a filtration process at vacuumwith a Buchnner funnel, using two cycles of filtering: first with 35mesh, and second with Watman No. 5 cellulose. In this way, thecontaminants retained with the clay are separated from the filtered oil.

Tables 3 and 4 show the results obtained, giving the characteristics ofthe used oils in the experiments, and the recovered lubricating baseoils after applying the experimental procedure.

TABLE 3 Initial Properties of the Used Motor Oil Flash Exp. pointDensity μ (cSt) Metals (ppm) Number (° C.) (gr/ml) 100° C. Ca Mg Zn FeCu Al Color Odor 1 203 0.81 13.2 1768 112 841 98 3 17 Dark Burned oilbrown 2 183 0.83 14.9 1826 129 972 96 5 12 Dark Burned oil black

TABLE 4 Final Properties of the Recovered Motor Oil After the ProcessFlash Exp. point μ (cSt) Metals (ppm) Number (° C.) 100° C. Ca Mg ZnColor Odor 1 196 11.2 50.2 3.1 12.4 Light Lubricating brown to base oilyellow 2 180 12.8 45.6 4.1 23.2 Reddish Lubricating chestnut base oil

CONCLUSION

The laboratory tests have shown that with the process described, aremoval takes place of metallic and organic contaminants of usedindustrial lubricating oils and those oils coming from internalcombustion motors. The level of removal is such that the recoveredlubricating oil bases can be used again with confidence in motor oils,automatic transmissions and other required uses. Our system is simpleand economic compared to other systems, and the quality of the recoveredoils is similar.

It is clear that the process and the product of the present inventionwill find wide use in the recovery and recycling of used industrial oilsas well as those oils coming as wastes from internal combustion motorsand transmissions. The foregoing describes only some embodiments of thepresent invention and obvious modifications to those skilled in the artcan be made thereto without departing from the scope of the invention.It is to be understood that the present invention is not limited to theembodiments described above, but encompasses any and all embodimentswithin the scope of the following claims.

1. A process for recovering used lubricating oil, comprising the stepsof: a) placing used lubricating oil and clay in a container where theyare put together in contact to form a mixture; b) heating the mixture toa suitable temperature for good sorption, with low effect of cracking;and c) removing and separating the lubricating oil from waste productscontaining the clay and contaminants of the used lubricating oil.
 2. Theprocess for recovering used lubricating oil according to claim 1,wherein a filter press system is used to separate the lubricating oilfrom the clay and contaminants, to form a clay cake that is discarded,obtaining oil essentially free from contaminants.
 3. The process forrecovering used lubricating oil according to claim 1, wherein the clayand contaminants are separated from the used lubricating oil using acentrifuge.
 4. The process for recovering used lubricating oil accordingto claim 3, wherein a filter press system is used to separate thelubricating oils from the clays and contaminants, to form a clay cakethat is discarded, obtaining oil essentially free from contaminants. 5.The process for recovering used lubricating oil according to claim 4,wherein the centrifuge is an industrial centrifugal machine.
 6. Theprocess for recovering used lubricating oil according to claim 5,wherein the centrifuge has a rotating screw, which allows it to separatemost of the clay from the lubricating oil to be recovered.
 7. Theprocess for recovering used lubricating oil according to claim 2,wherein the used lubricating oil is pre-filtered before forming themixture with the clay.
 8. The process recovering used lubricating oilaccording to claim 7, wherein the used lubricating oil is pre-treatedwith a flash type distillation, to separate a water residue from theused lubricating oil.
 9. The process for recovering used lubricating oilaccording to claim 8, wherein the mixture is heated with a systemincluding a heating jacket, wherein hot hydraulic fluid circulates totransfer heat.
 10. The process for recovering used lubricating oilaccording to claim 9, wherein the clay is acid-activated.
 11. Theprocess for recovering used lubricating oil according to claims 10,wherein the clay is a hybrid of hormite and smectite.
 12. The processfor recovering used lubricating oil according to claim 11, wherein thecontainer is a reactor, the hydraulic oil comes from a boiler, and aresidence time in which the mixture remains in the reactor variesaccording the type of used lubricating oil.
 13. The process forrecovering used lubricating oil according to claim 12, wherein themixture is heated to temperatures lower than 300 degrees Celsius. 14.The process for recovering used lubricating oil according to claim 13,wherein the mixture is heated to temperatures from 80 degrees Celsius to200 degrees Celsius.
 15. The process for recovering used lubricating oilaccording to claim 14, wherein after the residence time in the reactor,the mixture is poured out, and treated by a separation process.
 16. Theprocess for recovering used lubricating oil according to claims 15,wherein stirring rods are used to decrease the residence time of themixture in the reactor.
 17. The process for recovering of usedlubricating oil according to claim 16, wherein the volume of the clay islower than 60% of the volume of the used lubricating oil.
 18. Theprocess for recovering used lubricating oil according to claim 17,wherein the volume of clay is from 2% to 25% of the volume of the usedlubricating oil.
 19. The process for recovering used lubricating oilaccording to claim 18, wherein gases coming from the reactor are treatedwith trapdoors and filters to avoid atmospheric pollution.
 20. Recoveredused lubricating oil produced by a process comprising the steps of: a)placing used lubricating oil and clay in a container where they are puttogether in contact to form a mixture; b) heating the mixture to asuitable temperature for good sorption, with low effect of cracking; andc) removing and separating recovered lubricating oil from waste productscontaining the clay and contaminants of the used lubricating oil.